1. Field of the Invention
This invention relates generally to rotors for permanent magnet motors, and, in certain particular aspects, to novel methods for making rotors for permanent magnet motors.
2. Description of Related Art
Rotors for certain known permanent magnet rotors are constructed of a generally cylindrical body, e.g. made of iron or ferrous material, which may be of a solid or sintered metal construction or may be a laminated core, and around which are positioned a plurality of magnets. The magnets can be flat, bar magnets or accurately shaped with a contour conforming to the surface of the body. The magnets are adhered to the body, e.g. with fasteners, connectors, or with adhesives.
The prior art discloses various motors and methods for retaining magnets while making a rotor (see, e.g. U.S. Patents and applications U.S. Pat. Nos. 6,703,746; 6,324,745; 5,578,885; 5,040,286; 4,959,577; 4,588,915; 4,339,874; 3,858,308; 3,531,670; 3,221,194; Ser. Nos. 09/952,319, 09/2001; 10/867,402, 06/2004; 10/552,120, 05/2003; all incorporated fully herein for all purposes). One known technique involves positioning magnetic elements around a core and applying a KEVLAR (trademark) or fiberglass wrap or other bonding material to hold the magnets in place. Often an adhesive filler is employed to fill voids and provide a rigid structure.
Another technique for retaining magnets on an associated core in a permanent magnet rotor includes wrapping a relatively fine wire, under tension, around the magnetic elements followed by an adhesive or epoxy coating to protect the wires and “pot” the assembly. Another technique employs a cylindrically shaped shell or “can” which is assembled around the outer peripheral surfaces of the magnets.
Another known technique provides machined or cast pockets on a rotor core to receive and retain magnets in fixed rotational relation on a rotor (see, for example, U.S. Pat. Nos. 4,549,341; 4,617,726; and 4,625,135). Other techniques for retaining magnets in fixed relation on rotor cores include providing mutually engaging flat surfaces on cores and magnets (see, e.g. U.S. Pat. Nos. 4,656,379; 4,631,435; and 4,633,113). Another technique employs wedge shaped magnets which are retained in relatively complex pockets or slots formed in a rotor (see. U.S. Pat. Nos. 4,332,079; 4,339,874; and 4,336,649). Other techniques which have been employed to secure magnets to rotors include the use of adhesives, (see, e.g., U.S. Pat. No. 3,531,670) and the use of a cast aluminum core (see, e.g. U.S. Pat. No. 4,088,177).
There has long been a need, recognized by the present inventor, for an efficient and effective method for emplacing permanent magnets on a rotor body and for maintaining the magnets in position during manufacture of a rotor until a permanent retention method is in place.